Reactivity of Metals and Reactions of Acids and Bases

Reactions of Metals

• Reactive metals exhibit vigorous reactions when in contact with acids or water.

How Metals React with Acids

• Metals react with dilute acids to produce:

  • A salt
  • Hydrogen gas

• Reaction is represented as:

  $ext{Metal} + ext{Acid} <br /> ightarrow ext{Salt} + ext{Hydrogen}$

• Key Observations:

  • More reactive metals lead to faster reactions, e.g., sodium reacts explosively.
  • Experiment setup involves using dilute hydrochloric acid (HCl) or dilute sulfuric acid (H2SO4) with metals:
  1. Prepare boiling tubes with equal volumes of acid.
  2. Insert equal-sized pieces of metals (e.g., Mg, Zn, Fe).
  • Measure reaction speed by observing hydrogen gas bubble production.
  • Confirm hydrogen presence via burning splint test.
  • Mg produces the largest 'squeaky pop'.

• Reactions with Specific Metals:

  • Magnesium: Reacts vigorously with acids.
  • Reaction example:
    $ext{Mg (s)} + 2 ext{HCl (aq)} <br /> ightarrow ext{MgCl}<em>2 ext{(aq)} + ext{H}</em>2 ext{(g)}$
  • Zinc and Iron: React with acids but more effectively when heated.
  • Reaction example (Zinc):
    $ext{Zn (s)} + 2 ext{HCl (aq)} <br /> ightarrow ext{ZnCl}<em>2 ext{(aq)} + ext{H}</em>2 ext{(g)}$
  • Iron example:
    $ext{Fe (s)} + 2 ext{HCl (aq)} <br /> ightarrow ext{FeCl}<em>2 ext{(aq)} + ext{H}</em>2 ext{(g)}$

Reactions of Metals with Water

• General reaction:
  $ext{Metal} + ext{Water} <br /> ightarrow ext{Metal Hydroxide} + ext{Hydrogen}$

• Reactive Metals:

  • Potassium, Sodium, Lithium, Calcium react vigorously with water.
  • Mg, Zn, and Fe react with steam but less with cold water.
  • Example of a metal-water reaction:
    $ext{2Na} + 2 ext{H}<em>2 ext{O} ightarrow 2 ext{NaOH} + ext{H}</em>2$

• Non-reactive Metals:

  • Copper does not react with either water or steam.

The Reactivity Series

• Metals are organized in a reactivity series, from most reactive to least reactive:

  • Very Reactive: Potassium (K), Sodium (Na), Lithium (Li), Calcium (Ca), Magnesium (Mg)
  • Fairly Reactive: Aluminium (Al), Zinc (Zn), Iron (Fe)
  • Not Very Reactive: Copper (Cu), Silver (Ag), Gold (Au)

Displacement Reactions

• More reactive metals displace less reactive metals from compounds:

  • Example:
    $ext{Fe}<em>2 ext{O}</em>3 + 2 ext{Al} <br /> ightarrow 4 ext{Fe} + ext{Al}<em>2 ext{O}</em>3$

• Reactive metal displaces another in metal salts:

  • Example:
    $ext{CuSO}<em>4 + ext{Fe} ightarrow ext{FeSO}</em>4 + ext{Cu}$

Temperature Changes

• Displacement reactions can also be assessed by the change in temperature, with more reactive metals causing greater changes.

Reactions of Acids and Bases

• General reaction for neutralization:
  $ext{Acid} + ext{Base} <br /> ightarrow ext{Salt} + ext{Water}$

• Types of reactions:

  • Acid + Metal Oxide: Produces a salt and water (Example:
    $ext{2HCl} + ext{CuO} <br /> ightarrow ext{CuCl}<em>2 + ext{H}</em>2 ext{O}$)
  • Acid + Metal Hydroxide: Produces a salt and water.
  • Acid + Ammonia: Produces an ammonium salt.

Making Soluble Salts

• To create soluble salts:

  1. Use Acid + Insoluble Base: Heat acid, add insoluble base until neutralized.
  2. Filter excess solid, form a saturated solution.
  3. Crystallization occurs upon cooling.
     

• Example:
  $ext{CuO} + ext{H}<em>2 ext{SO}</em>4 <br /> ightarrow ext{CuSO}<em>4 + ext{H}</em>2 ext{O}$

• Ensure base is in excess to avoid leftover acid in the product.

Conclusion

• Understanding the reactions of metals, acids, and bases is essential for predicting chemical behaviors and forming compounds.
• Experiments highlight the properties of various metals across the reactivity series and their reactions with acids and bases.